1. Field of the Invention
The present invention relates to a method for manufacturing a board that includes a conductive pattern capable of obtaining high conductivity at a low sintering temperature, and a board that includes a conductive pattern that is manufactured by using the same.
2. Description of the Related Art
In a transparent substrate for display and a circuit board for electronic parts that are currently used, it is essentially required to form a conductive pattern. The conductive pattern is formed by mainly a photosensitive paste method or a photo etching method.
The photosensitive paste method includes the steps of coating a photosensitive paste on a substrate by using a screen printer, exposing UV using a photomask, and etching it by using an alkaline aqueous solution. A portion that is subjected to UV exposure by a photomask is not etched by an alkali aqueous solution because of photocrosslinking, and a portion that is not subjected to UV exposure is etched by an alkali aqueous solution because photocrosslinking is not carried out, such that an electrode pattern is formed. However, the forming of the electrode pattern by using the photosensitive electrode paste is disadvantageous in that it is difficult to control the degree of precision of a pitch and a width of the electrode.
In addition, the forming of the electrode pattern by using the photolithography method is mainly carried out by a process for entirely coating the electrode on the substrate or depositing the electrode on the substrate, and etching it. However, the photolithography method has problems in that a process time of depositing the electrode on the entire surface of the substrate, and costs of devices and materials are high while a thin film is formed, and there is an environmental contamination while etching is carried out.
Therefore, currently, as compared to the screen printing method or the photolithography method, an inkjet printing technology in which a mask is not required to form a fine pattern, it is not affected by the size of the board which will be printed, a printing time is short, and there is no problem in terms of environmental contamination is suggested.
The inkjet printing is a non-contact patterning technology in which a solution or a suspension solution is sprayed in drops of several to tens PL (pico liter) through a fine nozzle, and is advantageous in that the printing is freely carried out with a tens micrometer resolution.
Therefore, a technology in which a conductive pattern is formed on a substrate by using the inkjet printing is suggested. The conductivity of the conductive pattern that is formed on the substrate depends on the content of the metal particle included in the conductive ink composition, and in the case of when it is an ink that is generally used as a wire, the content of the metal particle in the conductive ink composition is in the range of 50 to 60 wt %. When the concentration of the metal particle is increased, the conductivity is increased, but since a reduction in dispersion property occurs according to this, there is a problem in stability of the conductive ink composition.
In general, if after the conductive ink composition that includes the inorganic metal particle is discharged to the substrate by using an inkjet printing method, a sintering process is carried out, 1) a solvent and an additive are removed, 2) melting occurs on the surface of the inorganic metal particle, and 3) the melted particle surfaces are fused, thereby causing necking between the inorganic metal particles. Through this process, a conductive pattern that includes the inorganic metal particles is formed. When the size of the inorganic metal particle that is used in the conductive ink composition is small, a sintering temperature is rapidly lowered, and in the case of when the particles having the size of about 50 nm, the conductivity can be shown at about 200° C. in the sintering process. However, as the method for reducing the size of the metal particle, in general, the sintering temperature of the conductive ink composition using the inorganic metal particles is determined at the temperature range of 200 to 300° C.
Meanwhile, in the case of the conductive ink composition that includes the organic metal particle, unlike the conductive ink composition that includes the inorganic metal particle, since metal particlization is carried out through a reduction process at a low temperature, the conductivity can be shown at the relatively low sintering temperature of about 150° C. However, in the case of the conductive ink composition that includes the organic metal particle, since the content of the metal is lower than that of the conductive ink composition that includes the inorganic ink, there are disadvantages in that the conductivity is low.